The conventional unit is proposed in FIGS. 3 to 5. FIG. 3 is a front view of the conventional door unit for an elevator. FIG. 4 is a view on arrow A-A shown in FIG. 3. FIG. 5 is a view on arrow B-B shown in FIG. 3.
With reference to the drawings described above, the numeral 101 indicates a landing door to be opened in opposite directions at an elevator landing entrance, 102 is a vertical frame of the entrance, 103 is an upper frame of the entrance, 104 is a sill. The vertical frame 102, the upper frame 103 and the sill 104 define an opening of the landing entrance. The numeral 105a indicates a smoke shielding member which is provided on a side portion of the door 101 and for closing a gap between the door 101 and the vertical frame 102, 105b is a smoke shielding member for closing a gap between the door 101 and the upper frame 103, 105c is a smoke shielding member which is inserted into a groove 104a of the sill 104 and for closing a gap thereof. The numeral 106 indicates a screw for mounting the smoke shielding members 105a, 105b, 105c. 
With the door unit thus constructed, the smoke shielding members 105a, 105b, 105c provided around the door 101 close gaps between the door and the entrance vertical frame 102, between the door and the entrance upper frame 103, and between the door and the sill 104 when the door is closed, to thereby prevent smoke from flowing into a hoistway even in the event of a fire, whereby the smoke is not distributed to other floor levels through the hoistway (e.g., JP-U No. 79184/1975, JP-A No. 112389/1988).
With the conventional unit, the smoke shielding members 105a, 105b, 105c are always in contact with members opposed to the smoke shielding members, so that the smoke shielding members are caused to wear with normally opening-closing the door, necessitating a proper maintenance work. Furthermore it is extremely difficult to smoothly open/close the landing door 101, to always cause trouble with sliding noise.
Furthermore there is a recent increase in the number of elevators having no machine room, i.e., elevators having equipments installed in the hoistway, such as a drive motor or a control panel to be a source of a fire, (so-called machine-roomless elevators). The interior of the building also becomes a source of fire when a fire breaks out. Therefore, there is a need to take measures for preventing properly the infiltration of smoke regardless of whether the smoke flow comes from the landing hall or from the hoistway. Furthermore, with the conventional unit, as shown in FIG. 6, three or more members are opposed, particularly, at a gap 107 between door stopping portions provided upward or downward of the landing doors 101 and at positions indicated by arrows in FIG. 18, so that it is indispensable to provide device to close the gaps for preventing properly the infiltration of smoke.
In view of the foregoing problems, an object of the present invention is to provide a door unit of an elevator having an excellent smoke shielding performance without causing trouble in a normal door opening-closing operation.